This invention relates to a mechanical excavator herein referred to as "the kind specified", provided on a tractor or other vehicle and which comprises a main boom, which at its lower end is pivotally connected to a king post assembly for movement up and down in a vertical plane, a dipper arm pivotally connected to the outer end of the boom for movement in a vertical plane and the dipper arm carrying or being adapted to carry a bucket or like tool, the king post assembly providing for pivotal slewing movement of the main boom about a vertical axis so that the main boom can be rotated from one side to the other of the centre line of the vehicle, the king post assembly being mounted upon a guide means extending transversely of the centre line of the vehicle, the king post assembly being moveable along the guide means, and fixing means releasably to fix the king post assembly relative to the guide means.
Hitherto, when it has been desired to slide the king post assembly along the guide means, this has been done either by lowering the excavator bucket to engage the ground and then slewing the main boom about said vertical axis to cause movement of the king post assembly along the guide means to a desired position, or the main boom has been slewed until it is at 90.degree. to the axis of the vehicle and the bucket then lowered to engage the ground, and the king post assembly being caused to move along the guide means by moving the dipper arm relative to the main boom (GB-959,790). Such methods of moving the king post assembly along the guide means are cumbersome and inconvenient.
An object of the present invention is to provide a mechanical excavator of the kind specified wherein the above mentioned problem is overcome or is reduced.